1. Field of the Invention
This application is directed to catalysts and catalyst supports prepared from mixtures of colloidal dispersions, such catalysts possess excellent catalytic and physical properties and also show excellent resistance to metal poisoning. These catalysts are highly useful in cracking processes, particularly when zeolites are incorporated. The catalyst supports in accordance with this invention may be used for other hydrocarbon conversion processes known to those of ordinary skill in the art.
2. Description of the Prior Art
In U.S. Pat. No. 3,912,619, Magee and Dougherty prepare silica-alumina hydrogel catalysts by neutralizing silicate with 30-90% of the required alumina, aging the hydrogel, adding further alumina and drying. Catalyst pore structure is specified in this case as a majority of pores between 45 and 125 A. In U.S. Pat. No. 3,933,621, high alumina, silica-alumina catalysts are prepared by cogelling silicate and aluminum sulfate by addition of base. Alumina content is 56-90%, preferably 65%. This patent also summarizes previous prior art for high alumina catalysts. In U.S. Pat. No. 4,010,116, cracking catalysts are prepared containing a peptized pseudoboehmite alumina gel, a synthetic micamontmorillonite, zeolite and a clay matrix component. Further, a series of recent patents deal with the use of "silica sols" in cracking catalysts: In U.S. Pat. No. 3,867,308 cracking catalysts are prepared by incorporating clay and zeolite in a silica sol prepared by rapid neutralization of sodium silicate with acid. An improvement is shown in U.S. Pat. No. 3,957,689 in which the rapid neutralization is performed with a mixture of sulfuric acid and aluminum sulfate. In U.S. Pat. No. 3,972,835, the silica sol is prepared by ion exchange of sodium silicate with an acidic ion exchange resin.
The effects of metal poisoning on the cracking performance of amorphous catalysts have been extensively investigated (U.S. Pat. No. 3,234,119); however, only recently have the effects been detailed for zeolitic cracking catalysts. As a result of such studies, it is now known that contaminant coke and hydrogen yields (coke and hydrogen produced by the metal poisoning) are lower on zeolitic than amorphous catalysts, but that metal activity is deactivated more rapidly on amorphous catalysts (Cimbalo et al., Oil & Gas Journal, May 15, 1972, p. 112). Therefore, a number of methods have been proposed to overcome the problems associated with the cracking of metal-contaminated feedstocks. For instance, U.S. Pat. No. 3,944,482 proposes the cracking of high metals content feedstock in the presence of a catalyst comprising 1 to 40 wt. % of a zeolite, having cracking characteristics, dispersed in a refractory metal oxide matrix having a largepore size distribution (about 50-100 A). Also, U.S. Pat. No. 3,711,422 proposes that metal poisoned cracking catalysts can be partially restored with antimony compounds and U.S. Pat. No. 3,977,963 proposes that the effects of metal poisoning can be negated with bismuth or manganese compounds.
However, none of the above prior art features the unique combination of the mixed colloidal sol and the catalyst pore structure as embodied herein.